The present invention relates generally to methods and apparatuses for stopping motors and disk storage unit having such apparatuses, and more particularly to a method and apparatus for stopping a DC motor and a disk storage unit having such an apparatus.
A brushless motor, which is a miniature precision DC motor without a brush, comprises a rotor comprising a permanent magnet and a stator comprising an armature. The brushless motor detects a position of the rotor and controls an armature voltage so that a torque angle constantly becomes .pi./2. It is required that the brushless motor used for a spindle motor of an optical disk have a high responsiveness. When the brushless motor is braked, a constant backward voltage is applied to the armature thereof until the motor decelerates to a predetermined rotating speed in response to a reverse rotation command. After the applied voltage is released, the motor then coast or naturally stops rotating from the predetermined rotating speed. On the other hand, the constant backward voltage may be applied to the motor until the motor reversely rotates, and then the applied voltage is released so as to naturally stop the motor. Incidentally, the strength of the applied voltage is constant irrespective of the load attached to the motor.
However, the above conventional method has the following disadvantages in that;
1. since there is a natural stopping period during which the motor naturally stops, it takes much time for the motor to completely stop.
2. the applied voltage is constant irrespective of the load applied to the motor. Therefore, if a plastic optical disk is applied to a motor brake apparatus corresponding to a glass optical disk, the plastic optical disk cannot step within a desired period.